1. Field of the Invention
The invention pertains to a self-pumping hydropneumatic shock absorber with internal level control, with an oil-filled working cylinder under the pressure of gas cushions and with a damping piston, which is attached to the end of a hollow piston rod and can slide back and forth in the working cylinder, the hollow space in the piston rod receiving a pump rod attached to the working cylinder, where oil is drawn from a reservoir space when the piston rod travels outward and into the working space when the piston rod travels inward, and where a control opening is provided in the pump rod to compensate for pressure differences between the working spaces.
2. Description of the Related Art
US 2005/0189186 discloses a self-pumping hydropneumatic shock absorber with internal level control wherein the damping piston is installed with freedom of axial movement in a working cylinder, where this damping piston is subjected to the pressure of a high-pressure gas cushion and of a low-pressure gas cushion. The damping piston is mounted on the end of a hollow piston rod, where the hollow space in the piston rod is designed as a pump space. A pump rod attached to the working cylinder projects into the hollow piston rod, so that, when the piston rod travels outward, it draws oil from a reservoir space, and when it travels inward, it transports this oil into the working space. When the vehicle reaches the desired level, a control opening is released, so that the pressures are equalized inside the shock absorber. The actual throttle in this case is designed as a bypass, where the flow of oil from the high-pressure space to low-pressure space is determined by a predetermined cross section of the bypass. In cases such as this where the cross section is fixed, the quantity of oil which can flow through the bypass is highly dependent on pressure. This pressure dependence is basically undesirable.